(a) Scope and application - (1) Scope. This appendix describes a method of classifying soil and rock deposits based on site and
environmental conditions, and on the structure and composition of the earth deposits. The appendix contains definitions, sets forth requirements, and
describes acceptable visual and manual tests for use in classifying soils.

(2) Application. This appendix applies when a sloping or benching system is designed in accordance with the requirements set forth in
1926.652(b)(2) as a method of protection for employees from cave-ins. This appendix also applies when timber shoring for excavations is designed as a
method of protection from cave-ins in accordance with appendix C to subpart P of part 1926, and when aluminum hydraulic shoring is designed in
accordance with appendix D. This Appendix also applies if other protective systems are designed and selected for use from data prepared in accordance
with the requirements set forth in 1926.652(c), and the use of the data is predicated on the use of the soil classification system set forth in this
appendix.

(b) Definitions. The definitions and examples given below are based on, in whole or in part, the following; American Society for Testing
Materials (ASTM) Standards D653-85 and D2488; The Unified Soils Classification System; The U.S. Department of Agriculture (USDA) Textural
Classification Scheme; and The National Bureau of Standards Report BSS-121.

"Cemented soil" means a soil in which the particles are held together by
a chemical agent, such as calcium carbonate, such that a hand-size sample
cannot be crushed into powder or individual soil particles by finger
pressure.
"Cohesive soil" means clay (fine grained soil), or soil with a high clay
content, which has cohesive strength. Cohesive soil does not crumble, can
be excavated with vertical sideslopes, and is plastic when moist.
Cohesive soil is hard to break up when dry, and exhibits significant
cohesion when submerged. Cohesive soils include clayey silt, sandy clay,
silty clay, clay and organic clay.
"Dry soil" means soil that does not exhibit visible signs of moisture
content.
"Fissured" means a soil material that has a tendency to break along
definite planes of fracture with little resistance, or a material that
exhibits open cracks, such as tension cracks, in an exposed surface.
"Granular soil" means gravel, sand, or silt (coarse grained soil) with
little or no clay content. Granular soil has no cohesive strength. Some
moist granular soils exhibit apparent cohesion. Granular soil cannot be
molded when moist and crumbles easily when dry.
"Layered system" means two or more distinctly different soil or rock
types arranged in layers. Micaceous seams or weakened planes in rock or
shale are considered layered.
"Moist soil" means a condition in which a soil looks and feels damp.
Moist cohesive soil can easily be shaped into a ball and rolled into small
diameter threads before crumbling. Moist granular soil that contains some
cohesive material will exhibit signs of cohesion between particles.
"Plastic" means a property of a soil which allows the soil to be
deformed or molded without cracking, or appreciable volume change.
"Saturated soil" means a soil in which the voids are filled with water.
Saturation does not require flow. Saturation, or near saturation, is
necessary for the proper use of instruments such as a pocket penetrometer
or sheer vane.
"Soil classification system" means, for the purpose of this subpart, a
method of categorizing soil and rock deposits in a hierarchy of Stable
Rock, Type A, Type B, and Type C, in decreasing order of stability. The
categories are determined based on an analysis of the properties and
performance characteristics of the deposits and the characteristics of the
deposits and the environmental conditions of exposure.
"Stable rock" means natural solid mineral matter that can be excavated
with vertical sides and remain intact while exposed.
"Submerged soil" means soil which is underwater or is free seeping.
"Type A" means cohesive soils with an unconfined, compressive strength
of 1.5 ton per square foot (tsf) (144 kPa) or greater. Examples of
cohesive soils are: clay, silty clay, sandy clay, clay loam and, in some
cases, silty clay loam and sandy clay loam. Cemented soils such as caliche
and hardpan are also considered Type A. However, no soil is Type A if:
(i) The soil is fissured; or
(ii) The soil is subject to vibration from heavy traffic, pile driving,
or similar effects; or
(iii) The soil has been previously disturbed; or
(iv) The soil is part of a sloped, layered system where the layers dip
into the excavation on a slope of four horizontal to one vertical (4H:1V)
or greater; or
(v) The material is subject to other factors that would require it to be
classified as a less stable material.
"Type B" means:
(i) Cohesive soil with an unconfined compressive strength greater than
0.5 tsf (48 kPa) but less than 1.5 tsf (144 kPa); or
(ii) Granular cohesionless soils including: angular gravel (similar to
crushed rock), silt, silt loam, sandy loam and, in some cases, silty clay
loam and sandy clay loam.
(iii) Previously disturbed soils except those which would otherwise be
classed as Type C soil.
(iv) Soil that meets the unconfined compressive strength or cementation
requirements for Type A, but is fissured or subject to vibration; or
(v) Dry rock that is not stable; or
(vi) Material that is part of a sloped, layered system where the layers
dip into the excavation on a slope less steep than four horizontal to one
vertical (4H:1V), but only if the material would otherwise be classified
as Type B.
"Type C" means:
(i) Cohesive soil with an unconfined compressive strength of 0.5 tsf (48
kPa) or less; or
(ii) Granular soils including gravel, sand, and loamy sand; or
(iii) Submerged soil or soil from which water is freely seeping; or
(iv) Submerged rock that is not stable, or
(v) Material in a sloped, layered system where the layers dip into the
excavation or a slope of four horizontal to one vertical (4H:1V) or
steeper.
"Unconfined compressive strength" means the load per unit area at which
a soil will fail in compression. It can be determined by laboratory
testing, or estimated in the field using a pocket penetrometer, by thumb
penetration tests, and other methods.
"Wet soil" means soil that contains significantly more moisture than
moist soil, but in such a range of values that cohesive material will
slump or begin to flow when vibrated. Granular material that would exhibit
cohesive properties when moist will lose those cohesive properties when
wet.

(c) Requirements - (1) Classification of soil and rock deposits. Each soil and rock deposit shall be classified by a competent person as
Stable Rock, Type A, Type B, or Type C in accordance with the definitions set forth in paragraph (b) of this appendix.

(2) Basis of classification. The classification of the deposits shall be made based on the results of at least one visual and at least one
manual analysis. Such analyses shall be conducted by a competent person using tests described in paragraph (d) below, or in other recognized methods
of soil classification and testing such as those adopted by the American Society for Testing Materials, or the U.S. Department of Agriculture textural
classification system.

(3) Visual and manual analyses. The visual and manual analyses, such as those noted as being acceptable in paragraph (d) of this appendix,
shall be designed and conducted to provide sufficient quantitative and qualitative information as may be necessary to identify properly the
properties, factors, and conditions affecting the classification of the deposits.

(4) Layered systems. In a layered system, the system shall be classified in accordance with its weakest layer. However, each layer may be
classified individually where a more stable layer lies under a less stable layer.

(5) Reclassification. If, after classifying a deposit, the properties, factors, or conditions affecting its classification change in any
way, the changes shall be evaluated by a competent person. The deposit shall be reclassified as necessary to reflect the changed
circumstances.

(d) Acceptable visual and manual tests. - (1) Visual tests. Visual analysis is conducted to determine qualitative information regarding
the excavation site in general, the soil adjacent to the excavation, the soil forming the sides of the open excavation, and the soil taken as samples
from excavated material.

(i) Observe samples of soil that are excavated and soil in the sides of the excavation. Estimate the range of particle sizes and the
relative amounts of the particle sizes. Soil that is primarily composed of fine-grained material material is cohesive material. Soil composed
primarily of coarse-grained sand or gravel is granular material.

(ii) Observe soil as it is excavated. Soil that remains in clumps when excavated is cohesive. Soil that breaks up easily and does not stay
in clumps is granular.

(iii) Observe the side of the opened excavation and the surface area adjacent to the excavation. Crack-like openings such as tension
cracks could indicate fissured material. If chunks of soil spall off a vertical side, the soil could be fissured. Small spalls are evidence of moving
ground and are indications of potentially hazardous situations.

(iv) Observe the area adjacent to the excavation and the excavation itself for evidence of existing utility and other underground
structures, and to identify previously disturbed soil.

(v) Observed the opened side of the excavation to identify layered systems. Examine layered systems to identify if the layers slope toward
the excavation. Estimate the degree of slope of the layers.

(vi) Observe the area adjacent to the excavation and the sides of the opened excavation for evidence of surface water, water seeping from
the sides of the excavation, or the location of the level of the water table.

(vii) Observe the area adjacent to the excavation and the area within the excavation for sources of vibration that may affect the
stability of the excavation face.

(2) Manual tests. Manual analysis of soil samples is conducted to determine quantitative as well as qualitative properties of soil and to
provide more information in order to classify soil properly.

(i) Plasticity. Mold a moist or wet sample of soil into a ball and attempt to roll it into threads as thin as 1/8-inch in diameter.
Cohesive material can be successfully rolled into threads without crumbling. For example, if at least a two inch (50 mm) length of 1/8-inch thread can
be held on one end without tearing, the soil is cohesive.

(ii) Dry strength. If the soil is dry and crumbles on its own or with moderate pressure into individual grains or fine powder, it is
granular (any combination of gravel, sand, or silt). If the soil is dry and falls into clumps which break up into smaller clumps, but the smaller
clumps can only be broken up with difficulty, it may be clay in any combination with gravel, sand or silt. If the dry soil breaks into clumps which do
not break up into small clumps and which can only be broken with difficulty, and there is no visual indication the soil is fissured, the soil may be
considered unfissured.

(iii) Thumb penetration. The thumb penetration test can be used to estimate the unconfined compressive strength of cohesive soils. (This
test is based on the thumb penetration test described in American Society for Testing and Materials (ASTM) Standard designation D2488 - "Standard
Recommended Practice for Description of Soils (Visual - Manual Procedure).") Type A soils with an unconfined compressive strength of 1.5 tsf can be
readily indented by the thumb; however, they can be penetrated by the thumb only with very great effort. Type C soils with an unconfined compressive
strength of 0.5 tsf can be easily penetrated several inches by the thumb, and can be molded by light finger pressure. This test should be conducted on
an undisturbed soil sample, such as a large clump of spoil, as soon as practicable after excavation to keep to a minimum the effects of exposure to
drying influences. If the excavation is later exposed to wetting influences (rain, flooding), the classification of the soil must be changed
accordingly.

(iv) Other strength tests. Estimates of unconfined compressive strength of soils can also be obtained by use of a pocket penetrometer or
by using a hand-operated shearvane.

(v) Drying test. The basic purpose of the drying test is to differentiate between cohesive material with fissures, unfissured cohesive
material, and granular material. The procedure for the drying test involves drying a sample of soil that is approximately one inch thick (2.54 cm) and
six inches (15.24 cm) in diameter until it is thoroughly dry:

(A) If the sample develops cracks as it dries, significant fissures are indicated.

(B) Samples that dry without cracking are to be broken by hand. If considerable force is necessary to break a sample, the soil has
significant cohesive material content. The soil can be classified as an unfissured cohesive material and the unconfined compressive strength should be
determined.

(C) If a sample breaks easily by hand, it is either a fissured cohesive material or a granular material. To distinguish between the two,
pulverize the dried clumps of the sample by hand or by stepping on them. If the clumps do not pulverize easily, the material is cohesive with
fissures. If they pulverize easily into very small fragments, the material is granular.

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